Sounds like wifi issue. If possible, hard wiring server with ethernet cable should take care of your problem.
Your mac can serve both as Roon core and endpoint, just not best for sonics. The Raspberry Pi is good choice at low price point. SOTM SMS 200 another choice,although more expensive, what I run.
Roon may end up being more expensive if you're not already using Tidal or Qobuz, the only two streaming music services interfacing with Roon. To repeat, you don't have to purchase any special equipment to run Roon, separate endpoint preferred.